The quality of water in a watershed reflects the condition of its associated ecosystems. Specifically, the Tayasan sub-watershed on Negros Island plays an important role in the water supply of the island region. Thus, it is important to assess its water quality in order to related the same with the general conditions of the sub-watershed. This study analyzes 14 water parameters that include physical, chemical, and biological aspects between 2015-2016 across the three sites of the watershed. Results show marked variations in depth, width, velocity, volume, biological oxygen demand (BOD), total suspended solids (TSS), and total coliform between seasons and across sites. It also identifies critical issues in the watershed such as burning of reforestation sites, conflicts in the community-based forest management agreement between the government and farming communities, encroachment of upland agricultural farming in steeped areas that were previously planted with endemics. The study concludes with the need for continuing reforestation, rehabilitation and maintenance of the Tayasan watershed from the effects of human activities in the remaining forest patches.
